Subversion Repositories psg16

PSG                     EQU             0xFFFF_FFFF_FFD5_0000
PSGFREQ0        EQU             0xFFFF_FFFF_FFD5_0000
PSGPW0          EQU             0xFFFF_FFFF_FFD5_0002
PSGCTRL0        EQU             0xFFFF_FFFF_FFD5_0004
PSGADSR0        EQU             0xFFFF_FFFF_FFD5_0006

;--------------------------------------------------------------------------
; Sound a 800 Hz beep
;--------------------------------------------------------------------------
;
Beep:
        subui   sp,sp,#16
        sm              [sp],r1/lr
        ori             r1,r0,#15               ; master volume to max
        sc              r1,PSG+128
        ori             r1,r0,#13422    ; 800Hz
        sc              r1,PSGFREQ0
        ; decay  (16.384 ms)2
        ; attack (8.192 ms)1
        ; release (1.024 s)A
        ; sustain level C
        setlo   r1,#0xCA12
        sc              r1,PSGADSR0
        ori             r1,r0,#0x1104   ; gate, output enable, triangle waveform
        sc              r1,PSGCTRL0
        ori             r1,r0,#25000000 ; delay about 1s
beep1:
        loop    r1,beep1
        ori             r1,r0,#0x0104   ; gate off, output enable, triangle waveform
        sc              r1,PSGCTRL0
        ori             r1,r0,#25000000 ; delay about 1s
beep2:
        loop    r1,beep2
        ori             r1,r0,#0x0000   ; gate off, output enable off, no waveform
        sc              r1,PSGCTRL0
        lm              [sp],r1/lr
        ret             #16